The present invention relates to a rotor having a squirrel cage and permanent magnets distributed around the circumference, with the rotor having a laminated core which extends over the entire rotor region and has longitudinally continuous rotor slots, with the squirrel cage passing through the rotor slots over the entire length of the laminated core, with the squirrel cage being formed with cage bars which are situated, preferably encapsulated, in the rotor slots and short-circuiting rings which connect the cage bars on both end faces of the laminated core, with the radius of a rotor region being reduced by at least the radial thickness of the permanent magnets. The invention also relates to an electric motor having a rotor of this kind and to a centrifugal pump which is equipped with an electric motor of this kind. The invention also relates to a method for operating an electric motor which is equipped with a rotor of this kind and to a method for producing a rotor of this kind and/or an electric motor of this kind.
German patent application no. DE 3609 750 A1 discloses an electrical machine which is in the form of a combined synchronous/asynchronous machine and has a stator and has a rotor which is arranged in a rotatable manner in the stator. The rotor is divided into three rotor regions as seen in the axial direction, at least one of said rotor regions being fitted with permanent magnets in the manner of a synchronous rotor and at least one being provided with a squirrel cage winding, which is situated in rotor slots, in the manner of an asynchronous rotor. The rotor has a laminated core which extends over all three rotor regions and has longitudinally continuous rotor slots and the radius of the laminated core having rotor slots is reduced by at least the radial thickness of the permanent magnet segments in the synchronous rotor region. The step rotor shown is a special design of a rotor which is correspondingly complicated in terms of manufacture and is associated with high costs. In addition, only the appropriate rotor regions are in each case used for the respective mode of operation, that is to say synchronous operation or asynchronous operation, in this rotor design. A design of this kind is therefore not advantageous in respect of the requirement for energy efficiency applicable today.
The rotor from U.S. Pat. No. 4,454,438 has permanent magnets which are arranged around the outer circumference of the rotor core. Either a magnet ring is mounted on the laminated core, or the permanent segments are arranged in pockets. A magnet ring is expensive and complicated to manufacture, and the permanent magnets which are to be pressed into pockets have to be produced with an accurate fit. This rotor also has a special design which requires a large number of complicated working steps in order to be produced.